The present invention relates essentially to the use of compositions based on isostearyl glycoside and isostearyl alcohol for the manufacture of cosmetic compositions with improved water resistance.
It is known that cosmetic compositions in the form especially of oil-in-water, water-in-oil or water-in-oil-in-water emulsions have a relatively inadequate water resistance.
It has been found for example that the efficacy of sun formulations, mascaras or baby care products decreases considerably after they have come into contact with water.
Different solutions have been proposed in the state of the art for overcoming this disadvantage and prolonging the action of such compositions over time.
Thus a first means of increasing the water resistance of cosmetic compositions consists in the incorporation, in a dose generally of between 1 and 5%, of various hydrophobic polymers and more particularly of vinylic copolymers such as the products marketed under the names ANTARON(copyright) or GANEX(copyright); high-molecular acrylic copolymers, for example the product marketed under the name DERMACRYL(copyright) LT,79 by NATIONAL STARCH; or polymers of vegetable origin such as the product marketed under the name GLOSSAMER(copyright) by TRI-K.
The polymers and copolymers used in this way as agents for improving the water resistance of cosmetic compositions are generally in the form of a paste or solid, so these products are relatively difficult to handle and necessarily have to be incorporated into a phase preheated to 80xc2x0 C.
Thus the ANTARON(copyright) products have to be melted and introduced into the fatty phase, with agitation, until they have dissolved, before they can be incorporated into the rest of the emulsion. Also, they have to be used under very precise HLB (hydrophilic-lipophilic balance) conditions and preferably in the presence of anionic emulsifiers.
Furthermore, the products of the DERMACRYL(copyright) type have to be at least 80% neutralized with an appropriate amount of base and have to be added slowly, with agitation. They can also be introduced into cosmetic compositions without prior neutralization, but it is then necessary to solubilize them either in alcohols or in ethanol.
Consequently, it is apparent that the use of polymers and copolymers as agents for improving the water resistance of cosmetic compositions creates practical difficulties which have limited their value.
A second means of improving the water resistance of cosmetic compositions consists in the incorporation of substantial amounts (greater than 40% by weight) of fatty phase containing conventional mineral oils and silicone phases such as silicone gums and particularly high-molecular polydimethylsiloxanes (cyclomethiconel dimethiconol), silicone resins (dimethicone/trimethylsiloxy silicate) or products of the phenyltrimethicone type.
The incorporation of such amounts of fatty phase presents difficult problems as regards the stabilization, particularly temperature stabilization, of the emulsions prepared. Oil exudation phenomena are also observed over time and these are unacceptable where cosmetic applications are concerned.
Also, the use of such amounts of fatty phases considerably increases the cost of these emulsions.
In general terms, all the means which have so far been envisaged in the state of the art for improving the water resistance of cosmetic compositions have produced emulsions which are difficult to spread and have a greasy and sticky feel.
Under these conditions, the object of the present invention is to solve the technical problem which consists in the provision of novel cosmetic compositions with improved water resistance which can be obtained relatively easily and inexpensively, are easy to spread and have a pleasant feel.
It has been discovered that the above-mentioned technical problem can be solved by the use of certain compositions based on isostearyl glycoside and isostearyl alcohol as agents for improving the water resistance of a variety of cosmetic compositions; it is this discovery which forms the basis of the present invention.
Thus, according to a first feature, the present invention relates to the use of a composition comprising 10 to 90% by weight, preferably 10 to 50% by weight and particularly preferably 10 to 40% by weight of an isostearyl glycoside with a degree of polymerization of between 1 and 3, and 90 to 10% by weight, preferably 90 to 50% by weight and particularly preferably 90 to 60% by weight of isostearyl alcohol, as an agent for improving the water resistance of a cosmetic composition.
The originality of the present invention compared with the prior art is that it makes it possible to obtain cosmetic compositions with improved water resistance without detracting from either the spreadability or the sensory properties (light feel, non-sticky character) of these compositions.
The compositions based on isostearyl glycoside and isostearyl alcohol which are used within the framework of the present invention are generally in liquid form. They are thus particularly easy to use and their application does not require any special precautions. In particular, these compositions can be applied cold and without additional stabilizer.
Within the framework of the present description, the expression xe2x80x9cisostearyl glycoside with a degree of polymerization of between 1 and 3xe2x80x9d is understood as denoting compounds of the formula
RO(G)x
in which:
R is an isostearyl radical;
x is a number between 1 and 3; and
G is a reducing glycopyranose or glycofuranose residue and preferably a glucose residue.
Advantageously, the degree of polymerization represented by x is between 1.05 and 2.5 and preferably between 1.1 and 2.
The isostearyl glycosides used within the framework of the present invention are not always pure.
In fact, they can also contain minor proportions of compounds of the same type in which the alkyl radicals have a longer and/or shorter chain, such compounds being derived especially from the fatty alcohols, generally of natural or synthetic origin, used as starting materials for the synthesis of these compounds.
xe2x80x9cMinor proportionxe2x80x9d is understood as meaning a maximum cumulative amount of xe2x80x9cimpuritiesxe2x80x9d of 5% by weight and preferably of 1% by weight, based on the total weight of the above-mentioned alkyl glycosides.
The compositions based on isostearyl glycoside and isostearyl alcohol which are used as agents for improving water resistance within the framework of the present invention can be prepared simply by mixing their constituents in desired predetermined proportions.
On the industrial scale, they will preferably be prepared by one of the two conventional methods used for the synthesis of alkyl polyglycosides and especially by reacting isostearyl alcohol in an acid medium with a saccharide which has an anomeric OH group, such as glucose or dextrose.
Such methods of synthesis are well known and have been widely described in the literature, particularly in documents WO 92/06778, WO 97/02091 or WO 97/18033.
If appropriate, this synthesis may be completed by operations involving neutralization, filtration, partial extraction or distillation of the excess fatty alcohol, or decolorization.
According to one particular characteristic of the invention, the above-mentioned compositions for improving water resistance comprise 10 to 25% by weight of an isostearyl glycoside with a degree of polymerization of between 1 and 10 3, and 90 to 75% by weight of isostearyl alcohol.
Advantageously, these compositions for improving water resistance will be used in an amount of between 0.2 and 10% by weight and preferably of between 0.5 and 5% by weight, based on the total weight of the cosmetic composition.
The cosmetic compositions with improved water resistance which are obtainable within the framework of the present invention can have a variety of forms, particularly the form of water-in-oil, oil-in-water or water-in-oil-in-water emulsions.
These emulsions may be prepared by the conventional methods described in the state of the art, for example by simple dispersion of a fatty phase in a hydrophilic phase in the case of oil-in-water emulsions, or by simple dispersion of a hydrophilic phase in a fatty phase in the case of a water-in-oil emulsion these operations being effected in the presence of an emulsifying system and optionally of a co-emulsifier and/or a stabilizer, it being possible for the dispersion to be prepared cold in view of the liquid nature of the composition based on isostearyl glycoside and isostearyl alcohol which is used as the agent for improving water resistance.
Of course, these emulsions can also comprise one or more compounds selected from humectants, for example glycerol, preservatives, for example the products known under the name SEPICIDE(copyright), colorants, perfumes, cosmetic active ingredients, mineral or organic sun filters, mineral fillers such as iron oxides, titanium oxides and talcum, synthetic fillers such as nylons and micropearls, and plant extracts.
The latter compounds may be introduced into the hydrophilic phase or into the fatty phase, depending on their affinity for these phases, either during the above-mentioned dispersion phase or optionally at a later stage.
As regards the nature of the oils which can be used as the fatty phase, reference may be made to the state of the art and especially the patent documents cited above.
According to a second feature, the present patent application aims to cover a method of improving the water resistance of a cosmetic composition which is essentially characterized in that it consists in incorporating into said cosmetic composition an effective amount of an agent for improving water resistance which is based on isostearyl glycoside and isostearyl alcohol, as defined above.